The cytotoxin alpha-sarcin behaves as a cyclizing ribonuclease
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Published on: December 15, 2017
J Lacadena1, A Martínez del Pozo, V Lacadena
1Departamento de Bioquímica y Biología Molecular I, Facultad de Química, Universidad Complutense de Madrid, Spain.
Abstract:
The hydrolysis of adenylyl(3'-->5')adenosine (ApA) and guanylyl(3'--> 5')adenosine (GpA) dinucleotides by the cytotoxic protein alpha-sarcin has been studied. Quantitative analysis of the reaction has been performed through reverse-phase chromatographic (HPLC) separation of the resulting products. The hydrolysis of the 3'-5' phosphodiester bond of these substrates yields the 2'-3' cyclic mononucleotide; this intermediate is converted into the corresponding 3'-monophosphate derivative as the final product of the reaction. The values of the apparent Michaelis constant (KM), kcat and kcat/KM have also been calculated. The obtained results fit into a two-step mechanism for the enzymatic activity of alpha-sarcin and allow to consider this protein as a cyclizing RNase.
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